The story revolves around a young boy named Sport Billy who is from the planet Olympus (a twin of Earth on the opposite side of the Sun) which is populated by athletic god-like beings. Billy himself has a magic size-changing gym bag - the Omni-Sack - which produces various tools as he needs them. He travels to Earth on a mission to promote teamwork and sportsmanship. Described by the show's theme song as a "hero from another planet", Billy battles the evil Queen Vanda and her gnome-like henchman, Snipe. Vanda's mission is to destroy all sports in the galaxy since fairness disgusts her.
Billy is assisted by two faithful companions, a girl named Lilly and a talking dog named Willy. The trio travel around in a time traveling spaceship, which resembles a giant wind-up clock, complete with a ringing bell, and mounted on two rocket engines. Each episode the trio travel through time to save a different Earth sport from Queen Vanda's grasp.